CN110569559A - Method for calculating maximum temperature tensile stress of end free lining plate in concrete construction period - Google Patents
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Abstract
The invention provides a method for calculating the maximum temperature tensile stress of an end free lining plate in the concrete construction period, which comprises the following steps: step 1, collecting data for calculating temperature control and crack prevention of concrete of the free lining plate at the end part; step 2, calculating the maximum temperature tensile stress sigma of the free lining plate concrete construction period at the end partmax＝‑0.342H+0.061W+0.051C+0.0515E+0.109T0‑0.036Tg‑0.0074Ta+0.126 Δ T-3.079. The method comprehensively and reasonably reflects the influences of main factors such as the thickness, the width, the parting length, the concrete strength grade, the surrounding rock deformation modulus, the pouring temperature, the air temperature in the tunnel during pouring construction, the winter lowest temperature in the tunnel, whether water is introduced for cooling, the water temperature and the like, and rapidly calculates the maximum temperature tensile stress of the free lining plate at the end part in the concrete pouring construction period at any period, thereby effectively realizing the temperature control target.
Description
Technical Field
The invention belongs to the technical field of temperature control and crack prevention of engineering structure concrete, and particularly relates to a method for calculating maximum temperature tensile stress of an end free lining plate in a concrete construction period.
Background
Cracks are one of the major diseases of concrete. In recent years, the construction of hydraulic and hydroelectric engineering is developed at a high speed, the scale and section size of a hydraulic structure are larger and larger, and the environmental conditions such as geology and the like are more and more complicated. As the height of the dam is increased, the drainage flow rate is higher and higher, and the concrete strength grade is higher. The large-section high-strength hydraulic lining concrete generates a large number of cracks without any exception as long as effective measures are not taken, and most of the cracks generate penetrating temperature cracks during construction (see fig. 1 and 2). The penetrating temperature crack seriously affects the safety of the engineering structure, the construction schedule, the leakage and even infiltration damage, the durability and the service life, the construction cost and the beauty, and can also induce the occurrence and the development of other diseases.
The existing relevant design specifications generally lack clear and specific regulations on the control of the temperature cracks of the lining concrete and the calculation method thereof, and have no clear temperature control standard. For example, the design Specification for hydraulic tunnels (DL/T5195-2004) requires only 11.2.6 items that the influence of the stress generated by temperature change, concrete drying and expansion and grouting pressure on the lining is solved by construction measures and constructional measures. Special studies should be made for the temperature stress generated in high-temperature areas.
at present, a finite element method is mainly adopted for temperature control anti-cracking design and temperature stress calculation of part of engineering lining concrete (such as a high-flow-rate flood discharging tunnel, a power generation tunnel diversion section and the like) which requires crack control in use in a construction period. After the structural design is finished, a construction temperature control anti-cracking scheme and a field construction highest temperature control standard are provided through simulation calculation analysis of temperature and temperature stress of a large number of schemes. By doing so, the precision is higher, and can optimize the construction scheme moreover. But the concrete mixing proportion and a large number of performance parameter tests need to be carried out firstly, and the test and the simulation calculation need to take more time; but also needs to spend more funds; the method can not be carried out when the construction mixing proportion is not determined and no concrete performance test is carried out; and the method is not suitable for the rapid adjustment of the scheme in the preliminary design stage and construction.
The above conditions are combined to show that the finite element method takes much time and cost for calculating the temperature stress during the construction period of the lining concrete at present, and cannot be applied to the initial design stage without concrete test results and the rapid adjustment of the scheme in construction.
In addition, due to different structural forms (circular, portal, flat and the like), the constraint inside the structure is obviously different, and the temperature stress generated under the same temperature action is also obviously different. Similarly, for a lining plate type structure, the free end part of the lining plate type structure has the advantages that the side slope lining, the stilling pool (including a plunge pool), the spillway and other bottom plate linings, the highway pavement concrete and the like are different, and compared with the hydraulic tunnel bottom plate lining concrete constrained by surrounding rock or side wall lining concrete, the temperature stress generated under the same temperature action has obvious difference due to different end part constraint conditions. The maximum temperature tensile stress calculation formula and the calculation result thereof may be different.
For example, the structure and the section size of a gate opening of a city are completely the same in a creek flood discharge hole and left and right bank non-pressure sections, the side wall lining concrete is poured firstly, and the left bank 1 is#、2#The non-pressure section of the flood discharge tunnel adopts an integral (one-time) pouring mode of a side wall and a top arch, and because the lining of the top arch and the side wall are integral, the lining of the side wall is strongly restrained, and simultaneously, the bottom is directly poured to a bottom rock mass and is also restrained by the rock mass; right shore 3#、4#the flood discharge tunnel adopts the side wall and the top arch to separately pour (2 times), namely the non-pressure section city gate tunnel lining structure is poured in 3 stages: pouring the side wall firstly, and not pouring the side wall to the bottom rock mass (the bottom is free); pouring a top arch; and finally, pouring a bottom plate. Therefore, the right bank 3#、4#The side wall lining poured in the flood discharge tunnel firstly has the top, the bottom and the upstream and downstream structure parting joints 4 circles which are free ends and are also free lining plates (only vertical plates, not horizontal plates) at the peripheral end parts. Patent 201910104904.1 proposes a method for calculating the maximum temperature tensile stress during the concrete construction of a side wall with a door-opening-shaped lining, but the method belongs to a method for calculating the maximum temperature tensile stress during the side wall construction in a way of integrally (once) pouring with a crown arch, and is suitable for the left bank 1#、2#The non-pressure section of the flood discharge tunnel adopts a mode of pouring the side wall and the top arch integrally (once), and the side wall (for example, the right bank 3) is poured separately (for more than 1 time) from the top arch#、4#Flood discharge tunnel lining side wall), because the end constraint conditions are different, the method cannot be applied, and a method for calculating the maximum temperature tensile stress in the construction period, which can be applied to the end free lining plate concrete, is urgently needed.
Disclosure of Invention
The invention is made to solve the above problems, and an object of the invention is to provide a method for rapidly calculating the maximum temperature tensile stress in the construction period of end free lining concrete, which can be used for optimizing and improving the temperature control measures for the end free lining concrete construction in real time to realize the temperature control target for finding problems and changing the construction technology, conditions and the like in the pouring construction process.
In order to achieve the purpose, the invention adopts the following scheme:
The invention provides a method for calculating the maximum temperature tensile stress of an end free lining plate in the concrete construction period, which is characterized by comprising the following steps of:
step 1, collecting data for calculating temperature control and crack prevention of concrete of the free lining plate at the end part;
Step 2, calculating the maximum temperature tensile stress sigma of the free lining plate concrete construction period at the end partmax(MPa)：
σmax＝-0.342H+0.061W+0.051C+0.0515E+0.109T0-0.036Tg-0.0074Ta+0.126 Δ T-3.079 (equation 1) in the above equation: h is the thickness (m) of the concrete of the end free lining plate; w represents the diagonal length (m) of the concrete of the free lining plate at the end part; c is the strength grade (MPa) of the concrete of the end free lining plate designed according to the age of 90 days; e is the deformation modulus (GPa) of the surrounding rock; t is0The casting temperature (DEG C) of the concrete of the end free lining plate; t isg＝35-TwThe water temperature effect value (. degree. C.) of the water cooling means is shown, and T is taken out without water coolingwAt 35 ℃, T in the presence of cooling waterwThe temperature of water is the temperature of water; t isaThe air temperature (DEG C) in the hole when the concrete is poured; delta T is the difference (DEG C) between the air temperature in the hole during pouring and the lowest air temperature in the hole in winter, and the delta T is Ta-Tmin，TminThe lowest temperature in the hole in winter.
And substituting the thickness, the angle line length, the concrete strength grade, the surrounding rock deformation modulus, the concrete pouring temperature, the air temperature in the cavity during concrete pouring construction, the winter minimum temperature in the cavity, whether water is introduced for cooling and the water temperature into the formula 1, and calculating the maximum temperature tensile stress of the concrete for pouring the door-cavity-shaped lining side wall lining in the construction period corresponding to the period.
Preferably, the method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining plate provided by the invention can also have the following characteristics: in step 1, the collected data for calculation includes: the method comprises the design and calculation results of temperature control and crack prevention, the concrete section size (thickness, width, parting length and the like) of the end free lining plate and the design data of the concrete strength grade of the lining plate, the environmental data comprising the deformation modulus of the surrounding rock under geological conditions, the annual change rule of the air temperature in the tunnel and the annual change rule of the water temperature, and the concrete pouring construction data comprising the temperature control measure scheme of concrete pouring construction, the pouring temperature, the air temperature in the tunnel during pouring construction, whether water is used for cooling or not and the water temperature of the concrete pouring construction data.
Preferably, the method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining plate provided by the invention further comprises the following steps: step 3, analyzing the maximum temperature tensile stress sigmamaxand (3) influencing the temperature control anti-cracking target and adopting corresponding control measures.
Preferably, the method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining plate provided by the invention can also have the following characteristics: the step 3 specifically comprises the following substeps: step 3-1, analyzing the temperature control anti-cracking data of the lining structure, particularly analyzing and knowing a temperature control anti-cracking target and crack control indexes, concrete strength and allowable tensile stress value, and an original temperature control measure scheme and allowable tensile stress value; step 3-2, comparing and analyzing tensile stress values: the calculated maximum temperature tensile stress sigmamaxComparing with the original temperature control measure scheme and the allowable tensile stress value thereof and the allowable tensile stress value of the concrete, and analyzing and checking whether the requirements are met; step 3-3, real-time improvement and optimization of the measure scheme: according to the comparative analysis result, if the tensile stress is rich (the tensile stress is small), optimizing and lightening the temperature control measures (if water cooling is not carried out), and if the tensile stress exceeds the control value, strengthening the temperature control measures (if cooling by adopting cooling water and water cooling is strengthened, and the pouring temperature is reduced).
Preferably, the present inventionThe method for calculating the maximum temperature tensile stress of the free end lining plate in the concrete construction period can also have the following characteristics: in the step 2, when the strength grade designed for the 28-day age is adopted by the lining side wall concrete, the strength grade designed for the 90-day age needs to be converted according to the specification; if the temperature of the air in the underground cave is increased by adopting the heat preservation of the hanging curtain in the construction period, T is determinedaAnd TminIncreasing the air temperature in the rear tunnel should be used. In addition, the thickness of the lining concrete is generally smaller, the water-cooling water pipes are arranged in a single row, namely, the formula is suitable for the situation that the water-cooling water pipes are arranged in the single row.
in addition, the invention can realize temperature control and crack prevention in an automatic control mode, for example, the data for calculation collected in the step 1 is input into a computer, and the computer firstly executes the step 2 to calculate the maximum temperature tensile stress sigmamaxThen, step 3 is executed, and the water cooling device is controlled to perform corresponding operations (stopping water supply, forced water cooling, adjusting water temperature, etc.).
In addition, the formula 1 proposed by the present invention is obtained based on the intensive study and analysis of the end free lining concrete structure and its related parameters. The free lining plate at the end of the udon flood spillway plunge pool shown in fig. 3 and relevant parameters thereof are taken as an example for explanation: based on the free lining plate at the end part and relevant parameters thereof, and combined with similar projects in China, a three-dimensional model as shown in figure 4 is established, and finite element method simulation calculation is carried out on various possible situations (119 schemes). The basic parameters and calculation schemes are shown in Table 1 below, where the maximum temperature tensile stress sigma is applied during the concrete lining construction periodmaxAlso shown in Table 1.
TABLE 1 calculation scheme of concrete temperature stress of end free lining plate and maximum temperature tensile stress
Maximum temperature tensile stress σ for the 119 solutions listed in Table 1 during end free liner concrete constructionmaxAnalysis and extensive study were carried out to obtain results consistent with the above formula 1.
Action and Effect of the invention
the method for calculating the maximum temperature tensile stress of the end free lining plate in the concrete construction period has a simple calculation formula, and can comprehensively and reasonably reflect the influences of main factors such as the thickness, the width, the parting length, the concrete strength grade, the surrounding rock deformation modulus, the pouring temperature, the air temperature in a tunnel during pouring construction, the lowest temperature in the tunnel in winter, whether water is fed for cooling, the water temperature and the like. The method can quickly calculate the maximum temperature tensile stress of the free lining plate concrete at the end part in any period of pouring (season) in the construction period, has small calculation error, and can be completely used for calculating the temperature tensile stress in the construction period of actual engineering, particularly for performing real-time quick calculation analysis in preliminary design and on-site construction period. The construction temperature control measures are optimized and improved based on the method, and the temperature control target can be effectively realized.
Drawings
FIG. 1 is a diagram of a concrete crack condition of a side wall lining a flood discharge tunnel of a three-plate stream power station in the background art;
FIG. 2 is a concrete crack situation diagram of a lining side wall of an underground water transportation tunnel of a permanent ship lock of the three gorges hydro-junction in the background art;
FIG. 3 is a schematic structural view of end free-lining concrete according to the present invention;
FIG. 4 is a three-dimensional finite element model diagram of end free-lay board concrete in accordance with the present invention;
FIG. 5 is a flow chart of a method for calculating maximum temperature tensile stress during concrete construction of an end free-lay panel according to an embodiment of the present invention;
FIG. 6 is a plan view of 851.50m elevation of end free-lined udder flood shed plunge pool elevation in accordance with an embodiment of the present invention;
FIG. 7 is a cross-sectional view of a bottom plate of a water lagoon of Udoud spillway tunnel with an end free lining plate according to a first embodiment of the present invention;
fig. 8 is a cross-sectional view (a) of an end free lining plate udder flood discharge tunnel plunge pool bottom plate and a finite element mesh model diagram (b) according to a first embodiment of the present invention;
Fig. 9 is a sectional view of the front protection slope (a) and the left protection slope (b) of the end free lining plate udder flood discharge tunnel plunge pool according to the second embodiment of the present invention;
Fig. 10 is a cross-sectional view (a) of the protection slope of the left bank of the udder flood discharge tunnel plunge pool with the end free lining plate according to the second embodiment of the present invention and a finite element mesh model diagram (b).
Detailed Description
The concrete embodiment of the method for calculating the maximum temperature tensile stress in the concrete construction period of the free end lining plate according to the invention is explained in detail by taking an example of calculating the temperature stress of the concrete of the free end lining plate of the water pad pond of the Wudongde flood discharge tunnel in combination with the attached drawings.
< Woodbe hydropower station basic data >
(1) overview
the Wudongde hydropower station mainly generates electricity and has the functions of flood control, shipping, sand blocking and the like. The installed capacity of the power station is 10200MW, the output is 3160MW, and the annual average power generation is 389.3 hundred million kW.h. The dam is a concrete hyperbolic arch dam, and flood discharge adopts a mode that the dam body mainly discharges flood and the shore flood discharge hole is assisted. The three flood discharging holes are all of tunnel type tunnels with pressure holes and then door-connected holes, and each tunnel type tunnel comprises a water inlet, a pressure hole section, a working gate chamber, a non-pressure hole section, an outlet section and an energy dissipation plunge pool, and the outlets adopt trajectory jet energy dissipation.
the flood discharge tunnel plunge pool is positioned at the downstream of a flood discharge tunnel outlet, a revetment and bottom plate concrete are required to be arranged on the plunge pool below the elevation 851.5m, and the plunge pool is arranged as shown in figure 6. The thickness of the gullet removing part of the bottom plate is about 3m, the height is from 792m to 795(794.6) m, and the flow direction gradient is 0.3%. Floor surface mixingThe concrete is C9040 (II) W8F150 abrasion-resistant concrete with the thickness of 50cm and the bottom of the abrasion-resistant concrete of C9025 (III) W6F150 concrete with a thickness of 2.5 m. Red copper water stops are uniformly arranged between the longitudinal and transverse seams of the construction blocks, and 2mm asphalt is coated on the surfaces of the seams. The lower part of the concrete is provided with a cushion layer with the thickness of 40 cm. The detailed structure is shown in FIG. 7
The design slope ratio of the front slope protection is 1:0.65, 1:0.593, 1:0.5 and 1:0.3 from top to bottom respectively, the design slope ratio of the left slope protection is 1:0.3, and the thickness of each side slope is 3 m. The tooth groove thickness of the downstream tail sill is 8.5m, the side slope thickness is 3m, the tail sill thickness is 7m, and the slope gradient is 1: 1. The concrete of the front side slope, the left side slope and the tail sill is divided into blocks according to about 10m, transverse seams are arranged according to steps, and asphalt with the thickness of 2mm is coated on the structural seam surfaces of the longitudinal and transverse seams. The specific structure is shown in figure 9.
(2) Data of ground temperature and air temperature
According to design data, the average perennial temperature value of the foundation rock mass of the water-cushioned pond bottom plate is as follows: 22.2 ℃. The ambient temperature is: the highest temperature in summer is 28 ℃, and the lowest temperature in winter is 14.0 ℃. The annual cycle change process of the air temperature is calculated by adopting a cosine function:
In the formula: t isaThe environmental temperature (DEG C) at the time t, A is the average temperature (DEG C) of the years, B is the annual variation (DEG C) of the temperature, and C is the number of days from the highest temperature to 1 month and 1 day. According to the measured air temperature data and the air temperature data of the local meteorological department, the environmental temperature is taken as A being 19.6 ℃, B being 7.3 ℃ and C being 210 d.
(3) Basic rock mass performance parameters
The foundation rock mass of the water-cushion pond bottom plate is II type, and the density of the rock mass is 2.75t/m3Poisson's ratio of 0.22, and deformation modulus of 32 GPa.
(4) Finite element method simulation calculation result of concrete lined on bottom plate of water-cushion pond
The concrete of the bottom plate of the water cushion pool of the flood discharge tunnel is constructed in summer, the outlet temperature of the concrete supplied by the Wudongde hydropower station is 14 ℃, and the pouring temperature in high-temperature seasons is 18 ℃. Pouring about 5 months and 1 day according to the construction schedule. A total of 2 temperature control calculation schemes were developed: 1) pouring at 18 ℃; 2) pouring at 18 ℃, cooling for 7 days by introducing water into water at 12 ℃, and covering the surface in winter for heat preservation. The results of the calculations are listed in table 2 below. According to the finite element method simulation calculation result, a temperature control measure scheme of pouring at 18 ℃ and cooling by water flowing at 12 ℃ for 7d is recommended for construction.
TABLE 2 summary table of temperature control characteristic values of representative points of the soleplate
(5) Finite element method simulation calculation result of concrete lining of left bank of plunge pool
The concrete for the protection slope of the left bank of the flood discharge tunnel is constructed in summer, the temperature of the concrete outlet supplied by the Wudongde hydropower station is 14 ℃, and the casting temperature in high-temperature seasons is 18 ℃. Pouring about 5 months and 1 day according to the construction schedule. A total of 3 temperature control calculation schemes were developed: 1) pouring at 18 ℃; 2) pouring at 18 ℃, and cooling for 7d by introducing water at 12 ℃; 3) pouring at 16 ℃, cooling for 7 days by introducing water into water at 12 ℃, and covering the surface in winter for heat preservation. The results of the calculations are listed in table 3. According to the finite element method simulation calculation result, a temperature control measure scheme of pouring at 18 ℃ and water cooling at 12 ℃ for 7d (encrypted water cooling and 3 layers arranged in the thickness direction) is recommended for construction.
Table 3 left bank slope lining concrete representative point temperature control characteristic value summary table
< example one > spillway tunnel water-filled pond baseboard lining concrete
A lining bottom plate of the flood discharge tunnel plunge pool is provided, the foundation rock mass is II type, and the thickness of the bottom plate is 3m (figures 7 and 8). The concrete on the surface of the bottom plate is C9040 (II) W8F150 abrasion-resistant concrete with the thickness of 50cm and the bottom of the abrasion-resistant concrete of C9025 (III) W6F150 concrete with a thickness of 2.5 m. The lower part of the concrete is provided with a cushion layer with the thickness of 40 cm. According to the finite element method simulation calculation, the lower layer has large thickness and low strength, and the temperature control and crack prevention are controlled by the lower layer. Therefore, when the method is adopted to calculate the maximum temperature tensile stress in the construction period and analyze temperature control anti-cracking measures, the method is carried out according to the following stepsThe total thickness of the concrete is taken as the lower layer concrete.
As shown in fig. 5, the method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining slab provided by the embodiment includes the following steps:
Step 1, collecting data for temperature control and crack prevention calculation of a lining structure:
the structural section of the lining bottom plate of the flood discharge tunnel plunge pool and the strength grade of concrete; environmental data, deformation modulus of geological condition surrounding rock, annual change rule of air temperature in the tunnel, annual change rule of water temperature and other basic data, as described above. Wherein the concrete thickness is calculated according to actual 3.0m, and the concrete strength is calculated according to main thickness C90And 25, calculating.
Step 2, calculating the maximum temperature tensile stress sigma of the free lining plate concrete construction period at the end partmax：
And (3) drawing up a calculation scheme: pouring construction is carried out in 5 months and 1 day in summer, and 1) pouring is carried out at 18 ℃ without water cooling; 2) pouring at 18 ℃, and cooling with water at 12 ℃ for 2 schemes.
Pouring the concrete in 5 months and 1 day in summer, and calculating T by a formula 2a19.76 deg.C, winter lowest air temp. Tmin12.3 ℃. According to the above data, H is 3.0m, W is 14.14m, C is 25MPa, E is 32GPa, T018 ℃.2 temperature control schemes (T) were plannedgCalculated by substituting the parameters at 0 deg.C, 23 deg.C and above into equation 1: non-aerated water cooling scheme σmax2.44 MPa; 12 ℃ refrigeration water through water cooling scheme sigmamax＝1.61MPa。
Step 3, analyzing the maximum temperature tensile stress sigmamaxThe method has the following steps of influencing a temperature control anti-cracking target, and taking corresponding control measures, wherein the method comprises the following substeps:
And 3-1, analyzing and calculating temperature control anti-cracking data of the lining structure of the bottom plate, particularly analyzing and knowing a temperature control anti-cracking target and crack control indexes, concrete strength and an allowable tensile stress value, and an original temperature control measure scheme and an allowable tensile stress value. The flood discharge tunnel has high flow velocity, and the bottom plate is lined with concrete to prevent harmful temperature cracks. Strength of concrete C9025, according to the design specification of a concrete structure, the standard value of the axial tensile strength is 1.78 MPa.
step 3-2, comparing and analyzing the tensile stress value, and calculating the maximum temperature tensile stress sigmamaxAnd comparing the temperature control measure scheme with the allowable tensile stress value and the allowable concrete tensile stress value, and analyzing and checking whether the requirements are met. 2 temperature control schemes are planned, and the stress sigma is calculated by the water-free cooling schememax＝2.44MPa，C9025 the standard value of the axial tensile strength of the concrete is 1.78MPa, and the standard value does not meet the requirement; stress sigma is calculated by a cooling scheme of cooling water with 12 ℃ cooling watermaxThe standard value of the axial tensile strength is 1.78 MPa.
And 3-3, improving and optimizing the measure scheme in real time, and optimizing and lightening the temperature control measure (if water cooling is not performed) if the tensile stress is abundant (the tensile stress is smaller) according to the comparison analysis result, and enhancing the temperature control measure (if the cooling is performed by adding cooling water and the pouring temperature is reduced) if the tensile stress exceeds a control value.
In the embodiment, a scheme of pouring at 18 ℃ and cooling with cooling water at 12 ℃ through cooling water is planned, and the stress sigma is calculatedmaxThe standard value of the axial tensile strength is 1.78MPa, which meets the requirement, and the margin is not large, so the proposal of the measures of pouring at 18 ℃ and cooling by cooling water at 12 ℃ is recommended.
the proposed scheme of the embodiment is compared with the simulation calculation result of the finite element method, and the recommended temperature control measure scheme is completely consistent with the simulation calculation result based on the finite element method.
The results show that: the calculated stress result of the formula 1 is consistent with the calculated value of the finite element method; the recommended temperature control measure scheme is completely consistent with the simulation calculation result based on the finite element method.
< example II > flood discharge tunnel plunge pool left bank revetment lining concrete
The basic data are the same as above. Lining C for slope protection of left bank of flood discharge tunnel plunge pool9025 concrete, the foundation rock mass is II type, and the thickness of the slope protection lining structure is 3m (figures 9 and 10).
As shown in fig. 5, the method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining slab provided by the embodiment includes the following steps:
step 1, collecting data for temperature control and crack prevention calculation of a lining structure: as above.
Step 2, calculating the maximum temperature tensile stress sigma of the free lining plate concrete construction period at the end partmax：
And (3) drawing up a calculation scheme: pouring construction is carried out in 5 months and 1 day in summer, and 1) pouring is carried out at 18 ℃ without water cooling; 2) pouring at 18 ℃, and cooling by introducing water at 12 ℃; 3) pouring at 16 ℃, and cooling by introducing water at 12 ℃; there are 3 schemes.
Pouring construction is carried out in 5 months and 1 day in summer, and the temperature T in the hole is calculated by a formula (2)aAt 19.76 deg.C, and the winter lowest air temperature Tmin12.3 ℃. According to the above data, H is 3.0m, W is 28.8m, C is 25MPa, E is 32GPa, T018 ℃.3 temperature control schemes (T) were plannedgCalculated by substituting the parameters of 0 deg.C, 23 deg.C and above into equation 1: 18 ℃ pouring non-water-cooling scheme sigmamax3.33 MPa; 18 ℃ pouring and 12 ℃ refrigerating water through cooling scheme sigmamax2.50 MPa; scheme sigma of 16 ℃ pouring, 12 ℃ water cooling and covering heat preservationmax＝1.86MPa。
Step 3, analyzing the maximum temperature tensile stress sigmamaxThe method has the following steps of influencing a temperature control anti-cracking target, and taking corresponding control measures, wherein the method comprises the following substeps:
and 3-1, analyzing and calculating temperature control anti-cracking data of the lining structure of the bottom plate, particularly analyzing and knowing a temperature control anti-cracking target and crack control indexes, concrete strength and an allowable tensile stress value, and an original temperature control measure scheme and an allowable tensile stress value. The flood discharge tunnel has high flow velocity, and the bottom plate is lined with concrete to prevent harmful temperature cracks. Strength of concrete C9025, according to the design specification of a concrete structure, the standard value of the axial tensile strength is 1.78 MPa.
Step 3-2, comparing and analyzing the tensile stress value, and calculating the maximum temperature tensile stress sigmamaxAnd comparing the temperature control measure scheme with the allowable tensile stress value and the allowable concrete tensile stress value, and analyzing and checking whether the requirements are met. 3 schemes, 18 ℃ pouring non-water-cooling scheme sigmamax3.33 MPa; 18 ℃ pouring and 12 ℃ refrigerating water through cooling scheme sigmamax2.50 MPa; scheme sigma of 16 ℃ pouring, 12 ℃ water cooling and covering heat preservationmax1.86 MPa. Are all greater than the axial reactanceThe standard tensile strength value is 1.78 MPa.
and 3-3, improving and optimizing the measure scheme in real time, and optimizing and lightening the temperature control measure (if water cooling is not performed) if the tensile stress is abundant (the tensile stress is smaller) according to the comparison analysis result, and enhancing the temperature control measure (if the cooling is performed by adding cooling water and the pouring temperature is reduced) if the tensile stress exceeds a control value. According to the calculation and analysis, the stress exceeding axial tensile strength standard value of the scheme 3 is 1.78MPa, the magnitude is very small (< 5%), and the scheme can be recommended to be used as a temperature control anti-cracking measure scheme. Namely, the suggested construction adopts the measures of pouring at 16 ℃, water cooling at 12 ℃ and covering, heat preservation and temperature control.
The proposed scheme of the embodiment is compared with the simulation calculation result of the finite element method, and the recommended temperature control measure scheme is completely consistent with the simulation calculation result based on the finite element method.
the results show that: the error between the stress value calculated by the formula 1 and the finite element method is small, and the recommended construction temperature control measure scheme is consistent with the simulation calculation result based on the finite element method, so that the method is reasonable, economic and effective.
The calculation formula is simple, and the influences of main factors such as the structural size of the bottom plate lining, the concrete strength grade, the surrounding rock performance (deformation modulus), the pouring temperature, the annual change of the air temperature in the tunnel, the air temperature in the tunnel during pouring, whether water cooling is conducted or not, the water temperature and the like can be comprehensively and reasonably reflected. The maximum temperature tensile stress of the free lining plate concrete at the pouring end part in any period (season) in the construction period can be rapidly calculated, the calculation error is small, and the method can be completely used for temperature crack control design of actual engineering, particularly preliminary design and real-time rapid design in the field construction period.
The above embodiments are merely illustrative of the technical solutions of the present invention. The method for calculating the maximum temperature tensile stress during the concrete construction of the end free lining slab according to the present invention is not limited to the contents described in the above embodiments, but is subject to the scope defined by the claims. Any modification or supplement or equivalent replacement made by a person skilled in the art on the basis of this embodiment is within the scope of the invention as claimed in the claims.
Claims (5)
1. a method for calculating the maximum temperature tensile stress of an end free lining plate in the concrete construction period is characterized by comprising the following steps:
Step 1, collecting data for calculating temperature control and crack prevention of concrete of the free lining plate at the end part;
Step 2, calculating the maximum temperature tensile stress sigma of the free lining plate concrete construction period at the end partmax：
σmax＝-0.342H+0.061W+0.051C+0.0515E+0.109T0-0.036Tg-0.0074Ta+0.126ΔT-3.079，
In the above formula: h is the thickness of the concrete of the free lining plate at the end part; w represents the diagonal length of the concrete of the free lining plate at the end part; c is the strength grade of the concrete of the end free lining plate designed according to the age of 90 days; e is the deformation modulus of the surrounding rock; t is0The pouring temperature of the concrete of the free lining plate at the end part is set; t isg＝35-TwT represents the water temperature effect value of the water cooling measure, and T is taken when water cooling is not performedwat 35 ℃, T in the presence of cooling waterwThe temperature of water is the temperature of water; t isaThe temperature in the hole when the concrete is poured; and delta T is the difference between the temperature in the hole during pouring and the lowest temperature in the hole in winter.
2. The method for calculating the maximum temperature tensile stress of the end free lining slab during the concrete construction period according to claim 1, wherein the method comprises the following steps:
Wherein, in step 1, the collected data for calculation includes: the lining plate design data comprises a temperature control anti-cracking design and calculation result, the concrete section size of an end free lining plate and the concrete strength grade, environment data comprising the deformation modulus of geological condition surrounding rock, the annual change rule of air temperature in a tunnel and the annual change rule of water temperature, and concrete pouring construction data comprising a concrete pouring construction temperature control measure scheme, pouring temperature, air temperature in the tunnel during pouring construction, whether water is fed for cooling and the water temperature.
3. The method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining slab as claimed in claim 1, further comprising:
Step 3, analyzing the maximum temperature tensile stress sigmamaxAnd (3) influencing the temperature control anti-cracking target and adopting corresponding control measures.
4. The method for calculating the maximum temperature tensile stress during the concrete construction period of the end free lining slab as claimed in claim 3, further comprising:
Wherein, the step 3 specifically comprises the following substeps:
Step 3-1, analyzing temperature control and crack prevention data of the lining structure, comprising the following steps: the method comprises the following steps of (1) controlling temperature control anti-cracking targets and crack control indexes, concrete strength and allowable tensile stress values, and calculating an original temperature control measure scheme and an allowable tensile stress value;
Step 3-2, comparing and analyzing tensile stress values: the calculated maximum temperature tensile stress sigmamaxComparing the temperature control measure scheme with the allowable tensile stress value and the allowable concrete tensile stress value, and analyzing and checking whether the requirements are met;
Step 3-3, real-time improvement and optimization of the measure scheme: according to the comparison and analysis result, if the tensile stress is smaller, the temperature control measures are optimized and relieved, and if the tensile stress exceeds the control value, the temperature control measures are enhanced.
5. the method for calculating the maximum temperature tensile stress of the end free lining slab during the concrete construction period according to claim 1, wherein the method comprises the following steps:
In the step 2, when the strength grade designed for the 28-day age is adopted for the lining side wall concrete, the strength grade designed for the 90-day age needs to be converted according to the specification; if the temperature of the air in the underground cave is increased by adopting the heat preservation of the hanging curtain in the construction period, T is determinedaAnd TminIncreasing the air temperature in the rear tunnel should be used.
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